Packaging laminate for a packaging container, as well as a packaging container produced from the packaging laminate

ABSTRACT

A packaging laminate for a retortable packaging container which comprises a paper or paperboard layer and outer, liquid-tight, heat-resistant layers of plastic on both sides of the paper or paperboard layer. Between the paper or paperboard layer and the outer plastic layer, the packaging laminate has at least one additional layer of a material possessing tightness properties vis-à-vis gases. In order to improve the preconditions for providing the packaging laminate with decorative artwork of printing ink with good print quality, the paper or paperboard layer has, on its one side, a printable coating of pigment and binder or adhesive, and on its other side a coating of starch.

TECHNICAL FIELD

The present invention relates to a packaging laminate for a packagingcontainer provided with decorative artwork and being of the type whichis produced from a prefabricated, flat folded packaging blank of thepackaging laminate, in that the packaging blank is first raised to anopen, tubular container carton whose one end is sealed by fold formingand thermosealing of the corresponding foldable end panels of thecontainer carton, for the formation of a liquid-tight, substantiallyplanar bottom closure, whereafter the container carton provided with thebottom is filled with a food and the other end of the filled containercarton is sealed by an additional fold forming and thermosealing of thecorresponding foldable end panels of the container carton, for theformation of a liquid-tight, substantially planar top closure, thepackaging laminate comprising a paper or paperboard layer whose one sidehas a printable coating of pigment and binder or adhesive in contactwith the paper or paperboard layer and decorative artwork of printingink applied directly on the printable coating by means of suitableprinting technology.

The present invention also relates to a packaging container of the typewhich, after filling and sealing, is to be subjected to ashelf-life-extending heat treatment in a retort with steam as heatmedium, the packaging container being produced from a prefabricated,flat folded packaging blank of the packaging laminate in that thepackaging blank is first raised to an open, tubular container cartonwhose one end is sealed by fold forming and thermosealing of thecorresponding foldable end panels of the container carton, for theformation of a liquid-tight, substantially planar bottom closure,whereafter the container carton, provided with a bottom, is filled witha food and the other end of the filled container carton is sealed by anadditional fold forming and thermosealing of the corresponding foldableend panels of the container carton, for the formation of a liquid-tight,substantially planar top closure.

BACKGROUND ART

A packaging laminate as well as a packaging container of the typedescribed above are known from, for example, International PatentApplication number PCT/SE2011/050978. The prior art packaging laminatehas a rigid, but foldable layer of paper or paperboard and outer,liquid-tight, heat-resistant layers of plastic on both sides of thepaper or paperboard layer. Between the paper or paperboard layer and oneof the outer, liquid-tight plastic layers, the prior art packaginglaminate has at least one additional layer possessing tightnessproperties vis-à-vis gases, in particular oxygen gas. One preferredexample of such a material possessing tightness properties vis-à-visgases is an aluminium foil, Alifoil, which moreover possesses theadvantage that it makes for thermosealing of the packaging laminate byso-called induction thermosealing which is a both rapid, simple andefficient sealing technology.

As a rule, a paper surface has a coarse as well as uneven surfaceprofile which makes it difficult to print direct on the paper orpaperboard surface with sufficiently uniform print quality. In order tocounteract this difficulty, the surface of the paper or paperboard layeron the side intended for printing is therefore provided with a printablecoating of pigment and binder or adhesive which renders the coarse paperor paperboard surface sufficiently even and smooth to be able to beprinted with good print quality.

A packaging laminate of the prior art type is produced from a web ofpaper or paperboard which, on its one side, has a printable coating ofpigment and binder or adhesive in contact with the surface of the web.The web is unwound from a magazine reel and led through a printingstation in which the web, on its coated side, is provided with thedesired decorative artwork of printing ink which is printed on theprintable coating of pigment and adhesive or binder.

From the printing station, the paper or paperboard web provided withdecorative artwork is led further to a lamination station in which theother or uncoated side of the web is provided with a layer of a materialpossessing tightness properties vis-à-vis gases, e.g. an aluminium foil,Alifoil, which is laminated to the paper or paperboard web.

From the lamination station, the laminated web is led finally to acoating station in which the web is coated with outer, heat-resistantlayers of plastic which are extruded on both sides of the web,whereafter the web is rolled up for further handling and use.

From a flat folded, tubular blank of the prior art packaging laminate, afinished packaging container of the type described by way ofintroduction is produced in the following manner. The flat-folded blankis first raised to an open packaging carton whose one end (e.g. thebottom end) is sealed by fold forming and thermosealing of thecorresponding foldable bottom panels of the packaging carton. Thepackaging carton, provided with a bottom, is filled with the relevantfood, whereafter the other end of the packaging carton (in this examplethe top end) is sealed by an additional fold forming and thermosealingoperation of the corresponding foldable top panels of the packagingcarton. The thus filled and sealed packaging container is thereafterready to be subjected to a shelf-life-extending heat treatment in aretort with steam as the heat medium.

Retortable packaging containers, of which one well-known commercialpackage is sold under the name Tetra Recart, has many valuableadvantages, not least for the consumer. They are mechanically strong andconfigurationally stable, at the same time as they are both easy to openand otherwise convenient to use. Moreover, they have the advantage over,for example, traditional conserve cans of metal and plastic that, afteremptying, they may readily be compressed to but minimum space savingflat sheets by simple flattening.

With the known packaging laminate it nevertheless not seldom happensthat problems with uneven print quality occur in connection withprinting of the pigment-coated paper or paperboard web. Problems of thistype may in many cases be attributed to fibre dust which is releasedfrom the freely exposed fibre surface of the paper or paperboard web(i.e. non-pigment coated) and transferred to the pigment coated surfacein connection with the pigment coated paper or paperboard web beingwound up onto a magazine reel. When the magazine reel is subsequentlyunwound for printing and conversion into finished packaging laminate,released fibre dust thus accompanies the laminate adhering to thepigment coating of the paper or paperboard web into the printing stationand thus impedes printing direct on the printable coating.

There is thus still a need for an improved packaging laminate, withoutconsequential dust-related problems which are associated with the priorart technology.

OBJECTS OF THE INVENTION

One object of the present invention is therefore to realise a packaginglaminate of the type described by way of introduction, without thoseproblems and drawbacks which are associated with the prior art packaginglaminate.

A further object of the present invention is to realise a packagingcontainer produced from the packaging laminate which, after filling andsealing, is to be subjected to a shelf-life-extending heat treatment ina retort using steam as heat medium.

BRIEF OUTLINE OF THE INVENTION

According to one aspect of the present invention, there will thus berealised a packaging laminate for a packaging container provided withdecorative artwork and produced from a prefabricated, flat foldedpackaging blank of the packaging laminate, in that the packaging blankis first raised to an open tubular container carton whose one end issealed by fold forming and thermosealing of the corresponding foldableend panels of the container carton for the formation of a liquid-tight,substantially planar bottom closure, whereafter the container cartonprovided with the bottom is filled with a food, and the other end of thefilled container carton is sealed by an additional fold forming andthermosealing of the corresponding foldable end panels of the containercarton for the formation of a liquid-tight, substantially planar topclosure, the packaging laminate comprising a paper or paperboard layerwhose one side has a printable coating of pigment and adhesive or binderin contact with the paper or paperboard layer, with a decorative artworkof printing ink applied by suitable printing technology direct on theprintable coating. The packaging laminate is characterised in that theother, or non-pigment coated side of the paper or paperboard layer has acoating of starch in contact with the paper or paperboard layer.

By providing a paper or paperboard web, whose one side is coated with aprintable coating of pigment and binder or adhesive, with an additionalcoating of starch on the other, or non-pigment coated side of the paperor paperboard web, the thus double-sided coated paper or paperboard webmay be wound up directly after production in a paper machine without therisk of releasing fibre dust and problems associated therewith in laterprinting of the web.

The coating of starch may be made extremely thin and in practice is of athickness of 1-5 g/m², preferably 3 g/m².

According to one practical embodiment of the packaging laminateaccording to the present invention, the printable coating on the oneside of the paper or paperboard layer comprises a combination of pigmentand adhesive or binder, as well as at least one further substancecapable of modifying the rheological properties of the coating. Examplesof such printable coatings are those which are described and disclosedin International Patent Application PCT/SE2011/050978.

Examples of usable binder or adhesive for the printable coating areselected from the group essentially comprising styrene butadiene latex,methyl metacrylate butadiene latex, polyacrylate latex, styrene acryllatex, polyvinyl acetate, polyvinyl alcohol, polysaccharides, starch,protein and combinations thereof.

Examples of usable substances capable of modifying the viscosity of eachrespective coating are selected from the group essentially comprisingprotein, polysaccharides, carboxy methyl cellulose (CMC), hydroxy ethylcellulose (HEC), alkali soluble acrylic polymer emulsion (ASE),hydrofobically modified alkali soluble acrylic polymer (HASE),polyurethane (PU), polyvinyl alcohol (PVOH) and starch.

Examples of usable pigment for both of the above mentioned surfacecoatings are selected from the group essentially comprising layeredsilicate mineral, hydratised magnesium silicate, calcium carbonate,titanium dioxide and kaolin.

According to one practical embodiment of the packaging materialaccording to the invention, at least 50% of the pigment in the printablecoating is calcium carbonate, while both the binder or adhesive and theabove mentioned rheology modifier comprise an acrylic copolymer.

In particular, the printable coating in the packaging material accordingto the present invention may contain:

-   -   an adhesive or binder of a styrene acrylic copolymer in an        amount of 10-20%, calculated on the weight of the composition;    -   pigment of layered silicate mineral clay and calcium carbonate        in an amount of 80-90%, calculated on the weight of the        composition; and    -   a substance capable of modifying the rheological properties of        the coating (“rheology modifier”) in a quantity of 0.1-1%,        calculated on the weight of the composition.

The coating of starch has, as has already been mentioned, a thickness orcoating quantity of less than 10 g/m², preferably approx. 5 g/m², andthe printable coating has a corresponding thickness or coating quantityof 15-20 g/m², preferably 20 g/m².

In order to protect the moisture and liquid-sensitive paper orpaperboard layer against penetration of moisture and liquid, thepackaging laminate according to the present invention has outer,liquid-tight layers of plastic which moreover should be sufficientlyheat resistant to withstand such temperatures to which a packagingcontainer produced from the packaging laminate is to be subjected whenthe closed packaging container, together with its filled contents, isheat treated in a retort with steam as heat medium. Examples of usableplastics for the outer, heat-resistant layers may be selected from thegroup essentially comprising high density polyethylene, linear lowdensity polyethylene, polypropylene and polyester.

The packaging laminate according to the present invention may besupplemented with at least one further layer of a material possessingsuperior tightness properties vis-à-vis gases, in particular oxygen gas.Examples of materials possessing desirable gas tightness properties maybe so-called barrier polymers, such as, for example, ethylene vinylalcohol copolymer and polyamide. Preferably however, this layer consistsof an aluminium foil, Alifoil, which renders the packaging laminatethermosealable by so-called induction thermosealing which is a bothrapid and efficient sealing technology.

According to another aspect of the present invention, there will berealised a packaging container which, after filling and sealing bythermosealing is, for purposes of extending its shelf-life, to besubjected to a heat treatment under pressure with steam as heat mediumin a retort.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will now be described in greater detailhereinbelow, with reference to the accompanying Drawings. In theaccompanying Drawings:

FIG. 1 is a schematic cross section of a packaging laminate according toone embodiment of the present invention;

FIG. 2 schematically illustrates a method of producing the illustratedpackaging laminate according to FIG. 1; and

FIG. 3 is a perspective view of a packaging container produced by foldforming and thermosealing of a packaging laminate according to thepresent invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 thus schematically illustrates a cross section of a packaginglaminate according to a first embodiment of the present invention. Inthe illustrated example, the packaging laminate 10 has a layer 11 ofpaper or paperboard and outer, liquid-tight, heat-resistant layers 12and 13, respectively, of plastic on both sides of the paper orpaperboard layer 11. Between the paper or paperboard layer 11 and one ofthe two outer, liquid-tight plastic layers 13, the packaging laminate 10moreover has a layer 14 of a material possessing tightness propertiesvis-à-vis gases, in particular oxygen gas, which is laminated to thepaper or paperboard layer 11 by the intermediary of a lamination layer15.

As illustrated schematically in FIG. 1, the paper or paperboard layer 11has, on its one side, a printable coating 16 of pigment and adhesive orbinder in contact with the surface of the subjacent paper or paperboardlayer 11. As was mentioned earlier, the printable coating 16 alsoincludes a substance capable of modifying the rheological properties ofthe coating 16.

It will further be apparent from FIG. 1 that the paper or paperboardlayer 11 has, on its other side, a coating 17 of starch in contact withthe paper or paperboard layer 11.

Usable examples of pigment for the printable coating 16 are, as has beenmentioned earlier, selected from the group essentially comprisinglayered silicate mineral, hydratised magnesium silicate, calciumcarbonate, titanium dioxide and kaolin.

Examples of usable binders or adhesives for the printable coating 16 areselected from the group essentially comprising styrene butadiene latex,methyl metacrylate butadiene latex, polyacrylate latex, styrene acryllatex, polyvinyl acetate, polyvinyl alcohol, polysaccharides, starch,protein and combinations thereof.

Examples of usable substances capable of modifying the rheologicalproperties of the printable coating 16 are selected from among the groupessentially comprising protein, polysaccharides, carboxy methylcellulose (CMC), hydroxy ethyl cellulose (HEC), alkali soluble acrylicpolymer emulsion (ASE), hydrofobically modified alkali soluble acrylicpolymer (HASE), polyurethane (PU), polyvinyl alcohol (PVOH) and starch.

In the illustrated embodiment of the packaging material 10 according tothe present invention, at least 50% of the pigment in the printablecoating 16 is calcium carbonate, while both the adhesive or binder andthe substance capable of modifying the rheological properties of thecoating comprise an acrylic copolymer.

The coating 17 of starch has, as was previously mentioned, a thicknessor coating quantity of less than 10 g/m², preferably less than 5 g/m²,such as for example 3 g/m², while the printable coating 16 has acorresponding thickness or coating quantity of 15-30 g/m², preferably 20g/m².

In order not to conceal decorative artwork of printing ink printed onthe printable coating 16 (schematically illustrated at reference numeral18), the outer, liquid-tight, heat-resistant plastic layer 12 of thepackaging material 10 should be transparent, so that the printeddecorative artwork 18 is clearly visible on visual inspection of thedecorated packaging laminate 10.

Examples of usable transparent plastics for the outer, liquid-tight,heat-resistant layer 12 may be selected from the group essentiallycomprising high density polyethylene (HDPE), linear low densitypolyethylene (LLDPE), polypropylene (PP) and polyester (PET).

Usable plastics for the outer, liquid-tight, heat-resistant layer 13 mayalso be selected from among the same group as the plastics mentioned forthe outer, liquid-tight, heat-resistant layer 12, i.e. from the groupessentially comprising high density polyethylene (HDPE), linear lowdensity polyethylene (LLDPE), polypropylene (PP) and polyester (PET).

Examples of materials possessing gas tightness properties for the layer14 may be so-called barrier polymers such as, for example, ethylenevinyl alcohol copolymer and polyamide. Preferably however, the layer 14is an aluminium foil, Alifoil, which renders the packaging laminate 10thermosealable by so-called induction thermosealing, which is a bothrapid, simple and efficient sealing technology.

The illustrated packaging laminate in FIG. 1 is produced using, forexample, the method which is schematically illustrated in FIG. 2. A web20 of paper whose both sides are coated with a surface coating ofpigment and binder or adhesive as described in greater detail inconnection with FIGS. 1 and 2, is unwound from a magazine reel 21. Thepaper web 20 is led through a printing station at A where the paper web20 is provided with the desired decorative artwork of printing inkwhich, by a suitable printing technology, is printed direct on thesurface of one of the two above mentioned coatings of pigment and binderor adhesive.

From the printing station A, the paper web 20 thus provided withdecorative artwork is led via bending rollers 22-25 to a laminationstation B where an aluminium foil 26 is converged with and laminated tothe non-decorated side of the paper web by means of a lamination layer27 which is extruded between the web 20 and the foil 26 in connectionwith these together being led through the nip between two laminationrollers 28.

The laminated paper web 20 is thereafter led further by the intermediaryof an additional bending roller 29 to a coating station C where the web20 is coated with outer, liquid-tight, heat-resistant coatings 30 and 31which are extruded on both sides of the web 20 when the web 20 is ledthrough the nip between two coating rollers 32.

From the coating station C, the laminated paper web 20 is thereafter ledfurther for rolling up onto a magazine reel 33 for further processingand use.

As was mentioned earlier, packaging containers may be produced from thepackaging laminate according to the present invention being of the typewhich, after filling and sealing, are to be subjected to ashelf-life-extending heat treatment in a retort with steam as the heatmedium. One example of such a retortable packaging container isschematically illustrated in FIG. 3. The illustrated packaging container300 is a substantially parallelepipedic package of the known packagingtype which occurs on the market under the trade name Tetra Recart.

The packaging container 300 is produced from a prefabricated, flatfolded packaging blank of the packaging laminate in that the packagingblank is first raised to an open tubular container carton. The one endof the container carton is sealed by fold forming and thermosealing othe corresponding end panels of the container carton for the formationof a liquid-tight substantially planar bottom closure. The containercarton thus provided with a bottom is filled with the relevant food,whereafter the other end of the filled container carton is sealed by afurther fold forming and sealing operation of the corresponding endpanels of the container carton for the formation of a liquid-tight,substantially planar top closure 301, as illustrated in FIG. 3.

1. A packaging laminate for a packaging container provided withdecorative artwork and produced from a prefabricated, flat foldedpackaging blank of the packaging laminate, in that the packaging blankis first raised to an open, tubular container carton whose one end issealed by fold forming and thermosealing of the corresponding foldableend panels of the container carton, for the formation of a liquid-tight,substantially planar bottom closure, whereafter the container cartonprovided with the bottom is filled with a food and the other end of thethus filled container carton is sealed by an additional fold forming andthermosealing of the corresponding foldable end panels of the containercarton, for the formation of a liquid-tight, substantially planar topclosure, the packaging laminate including a paper or paperboard layerwhose one side has a printable coating of pigment and binder or adhesivein contact with the paper or paperboard layer with decorative artwork ofprinting ink applied by a suitable printing technology on the printablecoating, wherein the other side of the paper or paperboard layer has acoating of starch in contact with the paper or paperboard layer.
 2. Thepackaging laminate as claimed in claim 1, wherein the coating of starchis of a thickness or coating quantity of less than 10 g/m².
 3. Thepackaging laminate as claimed in claim 1, further comprising outer,liquid-tight, heat-resistant layers of plastic on both sides of thepaper or paperboard layer.
 4. The packaging laminate as claimed in claim3, wherein the outer, liquid-tight plastic layers are selected from thegroup essentially comprising high density polyethylene, linear lowdensity polyethylene, polypropylene and polyester.
 5. The packaginglaminate as claimed in claim 1, further comprising a layer of a materialpossessing tightness properties vis-à-vis gases.
 6. The packaginglaminate as claimed in claim 5, wherein the layer possessing gastightness properties is an aluminium foil.
 7. A parallelepipedicpackaging container of the type which, after filling and sealing, is tobe subjected to a shelf-life-extending heat treatment in a retort withsteam as heat medium, the packaging container being produced from aprefabricated, flat folded packaging blank of a packaging laminate asclaimed in claim 1, in that the packaging blank is first raised to anopen, tubular container carton whose one end is sealed by fold formingand thermosealing of the corresponding foldable end panels of thecontainer carton, for the formation of a liquid-tight, substantiallyplanar bottom closure, whereafter the container carton, provided withthe bottom, is filled with a food and the other end of the thus filledcontainer carton is sealed by an additional fold forming andthermosealing of the corresponding foldable end panels of the containercarton, for the formation of a liquid-tight, substantially planar topclosure.
 8. The packaging laminate as claimed in claim 1, wherein thecoating of starch is of a thickness or coating quantity of less than 5g/m².
 9. The packaging laminate as claimed in claim 1, wherein thecoating of starch is of a thickness or coating quantity of 3 g/m². 10.The packaging laminate as claimed in claim 1, further comprising a layerof a material possessing tightness properties vis-à-vis oxygen gas.